In a conventional telephone exchange system, telephones each having a recording/playback function are used as extension telephones connected to the system in order to record the audio of a telephonic communication that is in progress. This makes it possible for each extension to individually record and/or playback the audio of the communication. In another conventional telephone exchange system, the system is provided with a memory device shared by each extension telephone, the storage area of the memory device is divided among the extensions, and a telephonic communication is recorded in or played back from an area that has been designated from an extension telephone by an operation performed at this telephone.
If the former arrangement having a recording/playback function for every extension is adopted, it raises the cost of the telephone exchange system. In order to convey the contents of a recording as is from one extension telephone to another, a troublesome operation is required in which the recording medium such as a recording tape is handed over to the party for which the message is intended or the recording is re-recorded on the recording medium possessed by this party.
In the latter case where the storage area of one memory device is apportioned to each of a plurality of extension telephones and used to record and/or playback a telephonic communication, the storage areas used are fixedly assigned to the telephones. Consequently, the storage capacity for a particular user may be inadequate or, even if the storage capacity for a user is more than enough, it cannot be used by another telephone. Thus, the storage areas cannot be effectively exploited by the system as a whole.
Further, in conventional telephone exchange systems, when a message is requested to be delivered to someone who is absent, and the party who is to receive the message happens to return to the location of his or her own telephone while the recording is in progress, this individual may not know that the message intended for him or her is being recorded and will not be able to engage the calling party who is in the process of leaving the message.
In addition, since the starting time of a recording cannot be determined in conventional telephone exchange systems, one may not respond soon enough to a recorded message, to the detriment of a commercial transaction or the like.